Shoes, in particular soccer shoes, have two functions: first, to increase the grip of the shoe on a playing surface, e.g., a field, by providing profile elements, such as studs; and second, to improve the control of the ball by a player and the delivery of sharp shots to the ball, by virtue of the design of the upper of the shoe. For example, it is known to provide the surface of the instep of a soccer shoe with friction enhancing elements in order to improve control of the ball by the player.
A further design objective for a soccer shoe, similar to a running shoe, is to make the shoe as lightweight as possible. A reduction in the weight of the shoe reduces the power of the player necessary for the course of movements, since the forces of inertia to be surmounted increase proportionally to the mass of the shoe. A lightweight shoe needs less power for being moved than a heavy shoe. This applies for both running and kicking a ball. The increasing use of lightweight, but highly stable plastic materials, facilitates the manufacturing of shoes with an overall weight of less than 300 grams (g).
For training purposes, however, it is known to provide additional weights in the shoes for selectively strengthening the muscles of the leg and the foot. Examples of this concept can be found in published U.S. Patent Application Nos. 2001/0000835 A1 and 2002/0017039 A1, as well as in issued U.S. Pat. No. 5,758,435, the entire disclosures of which are hereby incorporated by reference herein. For example, each application/patent discloses training weights arranged in a wide variety of sole areas of the shoes. With respect to soccer shoes, it is specifically known from issued U.S. Pat. No. 5,901,473, the disclosure of which is hereby incorporated herein by reference in its entirety, to increase the weight of the shoe during training by using particularly heavy studs on the shoe. Thus, the player can develop an additional power reserve without having to use a different shoe. For a game, however, the heavy training studs are replaced by common lightweight studs in order to obtain the above-described advantages of a particularly lightweight shoe.
A shoe provided with additional weights may in the long term increase the overall performance of an athlete; however, a direct improvement of the shooting power of a player or the player's feel for the ball is not obtained by this approach. There is, therefore, a need for a soccer shoe that allows a player to shoot the ball in a sharper and more controlled manner than with conventional soccer shoes.